Mosquitoes are the most medically important group of insects, both from the viewpoint of the numbers of disease agents they transmit and the magnitude of the health problems these diseases cause world-wide. It is becoming increasingly clear that the vectorial capacity of adult mosquitoes is related to the dietary resources available to the larvae in their natural habitats. The current trend toward the use of control agents what are ingested by mosquito larvae emphasizes the urgent need for studies on their feeding behavior and nature of their dietary resources. This proposal is directed at furthering our knowledge of natural feeding ecology of mosquito larvae. Our specific aims are: 1) to characterize, compare, and contrast the feeding strategies of Aedes triseriatus and Anopheles quadrimaculatus larvae in natural and simulated-natural environments; 2) to assess the nature and assimilation of resources ingested by larval mosquitoes as related to resource partitioning in habitats; 3) to examine and determine the relationship between larval habitat and adult productivity, based on the spatial and temporal distribution of dietary resources in natural habitats. Laboratory and field experiments include the following methodologies: 1) comparative analysis of larval feeding behaviors in field and simulated field conditions; 2) videomicroscopy and high speed microcinematography to analyze mouthpart movements as related to particle capture and feeding strategies; 3) X-ray diffraction and epifluorescent microscopy to determine the size and nature of particles ingested by larvae; 4) food choice experiments using natural foods (bacteria, protozoa, algae, detritus); 5) quantitative and qualitative characterization of the total organic pool of particulate and dissolved carbon; 6) 14-C labeling techniques to investigate the role of microorganisms, glycocalyces and structural components of particulates to larval growth; 7) microcosm studies to assess growth rates of larvae under manipulated dietary resources and larval mosquito densities in treeholes, tires, pond surface films and field microcosms to determine their effects on larval growth and adult productivity. Results of these studies will provide valuable information on the feeding behavior, diet, growth and production of larval mosquitoes in their natural habitat, which can then be related to vectorial capacity of adults, and will greatly assist in the formulation of new materials for field-use in the control of mosquitoes.